As is shown in FIG. 1, a basic toner container for the present invention has an opening part (outlet) 11 for discharging toner particles at one end, which is sealed doubly by an outer cap 20 and an inner cap 30.
One example of the base toner container for the present invention is described below using FIG. 1, which is an illustration showing, however, a structure of conventional toner container. As is shown in FIG. 1, a cylindrical container main body 10 has a neck part 15 of a slightly smaller diameter between the opening part 11 and itself. The neck part 15 is connected to a toner housing part 16 of a larger diameter than it via a shoulder part 14 of a gentle curve, which makes movement of toner to the opening part 11 smooth. The container main body 10 has a guide groove 13 formed in a spiral manner for sending the toner inside to the opening part (discharge spout) 11 by a rotation of the container main body 10. The guide groove 13 is so shaped that it forms a ridge projecting into inside of the container main body.
The outer cap 20 has a female screw part 21 shaped integrally on an inner surface of the wall so that the female screw part 21 screws together a male screw part 12 shaped on the outer surface of the wall of the opening part 11 of the toner container main body 10.
The inner cap 30 has a tapering structure with slightly slender end and slightly large head so that the inner cap seals the opening part 11 when it is pushed into the inner opening part (discharge spout) 11 of the toner container main body 10 and opens the opening part 11 when it is pulled out of the opening part 11. The inner cap 30 has a opening entering part 31 shaped with a flexible resin material. The degree of tapering of the inner cap is so slight that it is difficult to recognize the tapering at a glance. On the outer surface of the opening entering part 31, a plurality of rubbery transverse ribs 33 are circumferentially formed to seal the opening part 11. In this example, they are 3 ribs, i.e., an upper rib 33a, a middle rib 33b, and a lower rib 33c. Further, an inner cap head part 34 forming a base of the tapering opening entering part 31 has a flange part 35 which is equipped with a circumferential fold rib 36 at the outer edge of the flange part 35. A flexible edge of the fold rib 36 is in close contact with a ceiling surface 11a to seal the toner container main body. In other words, the inner cap 30 seals the opening part 11 of the toner container main body by two sealing means, i.e., a plurality of rubbery transverse ribs 33 placed on the tapering opening entering part 31 and a fold rib 36. In FIG. 1, a knob part 37 is indicated. The knob part 37 is held by a chuck mechanism placed in an image forming apparatus, when the toner container is disposed at a fixed position in the image forming apparatus to have its sealing broken. By this process the inner cap 30 is immobilized, and removed from the container main body 10 which is moved by a movement mechanism in the image forming apparatus to the direction in which the container main body 10 is leaving away from the inner cap 30. The knob part is particularly useful also in such an inner cap removing step. Such an inner cap removing system is disclosed in detail in our Patent Literatures 1 and 2.
The sealing of the toner container (bottle) is excellent, and the toner container causes no toner leakage. However, the toner container easily causes a difference between the inner pressure and an atmospheric pressure due to an environmental change, such as a temperature change at the storage site of the toner container. Particularly when the toner container is stored at a cold site such as a storage plant in a cold district, the inner pressure of the toner container becomes negative. When the storage period becomes long, cold air is incorporated into the toner container till the inner pressure of the toner container reaches the atmospheric pressure, in spite of the excellent toner sealing ability which is not a complete sealing ability to air. When the toner container in which cold air is incorporated till the inner pressure becomes the atmospheric pressure is brought into a heated room, the inner pressure of the toner container increase as the temperature rises, which causes a drawback of inner cap departure when an outer cap is removed, and the inner pressure increases to a pressure level at which the inner cap can not seal the air in the toner container (Patent Literature 3).
A toner container described in Patent Literature 4 with an inner cap being fixed to a container opening using a screw system causes no drawback of inner cap departure, however, has difficulty in processing of the container opening and the inner cap and requires a complex mechanism for removing the inner cap in an electrophotographic apparatus.
To solve the above problem, a toner container is disclosed in Patent Literature 5 that has a mechanism, placed between a toner container opening and an inner cap, to evacuate an excessive amount of air in the toner container depending on the storage conditions of the toner container. However this toner container shows considerable variation in degree of decreases in inner pressure and costs more for further processing.
In addition this toner container is controlled so that an excessive amount of air is evacuated from an interspace between the inner cap and an outer cap by controlling the tightening torque between the toner container and the outer cap with a low value, which can loosen the outer cap due to drop impact, shaking impact or in handling of the toner container in a cause of transportation of the product, leaving a problem with control of tightening torque of the outer cap.
Further a toner container is disclosed in Patent Literature 6, which is provided with a mechanism that a pressure valve with an elastic body member is placed in a casing part to control the inner pressure responding to an inner pressure change. However, in this toner container, the valve opens at an inner pressure of 0.01 kgf/cm2 or more, which may cause toner leakage when the toner container is laid or turned bottom up, and may cause toner leakage even in normal handling of the toner container by users and during transportation of the toner container.
[Patent Literature 1] Japanese Patent (JP-B) No. 3509385
[Patent Literature 2] Japanese Patent Application Laid-Open (JP-A) No. 2004-110049
[Patent Literature 3] JP-A No. 09-96959
[Patent Literature 4] JP-A No. 08-220857
[Patent Literature 5] JP-A No. 2004-279978
[Patent Literature 6] JP-A No. 2001-75349